Fuze



J. ROSSELET Sept. 1, 1953 FUZE Filed May 27, 1949 Don: wd'er Jean KoSSe/el' 2 Arl'or'uLy Patented Sept. 1, 1953 assess.

FUZE

Jean Rosselet, Geneva, Switzerland Application May 27, 1949, Serial No. 95,698 In Switzerland May 28, 1948 1 Claim.

The present invention concerns a controlling or actuating mechanism for fuzes of rotation projectiles. The said mechanism is preferably utilised as a setting mechanism, and will be described as such. In the known setting mechanisms movable elements are utilised, such as balls, cylinders, pistons, inertia masses, split rings, which, being displaced by centrifugal force, occasion either the liberation of a striker which is blocked when at rest, or the liberation of an intermediate member. The fuze is set when percussion is possible.

All the devices at present employed have the disadvantage of functioning practically instantaneously, the fuze being set as soon as the projectile leaves the muzzle of the barrel.

The mechanism according to the present invention furnishes a delay to the setting, and thus provides a material security of trajectory.

The mechanism according to the invention is characterised by the feature that it comprises at least one movable setting element, which, under the impulse of centrifugal acceleration and retardation acceleration, traverses, by a rolling movement, a definite path on a first ramp, and then effects the setting in moving over a second ramp.

Some forms of construction of a mechanism according to the invention are illustrated by way of example in the accompanying drawings, in which:

Figure 1 represents in axial section a first mechanism;

Figure 2 is a cross section of the mechanism on the line II in Figure 1;

Figure 3 illustrates the operation of the mechanism;

Figure 4 represents in section a detail of a mechanism;

Figure 5 represents in axial section a projectile fuze comp-rising a mechanism according to the invention;

Figure 6 is a cross section of the mechanism on the line IIII in Figure 5;

Figure '7 is a cross section of the fuze on the line IIIIII in Figure 5; and.

Figure 8 represents in perspective an element of the mechanism.

The mechanism illustrated in Figures 1, 2 and 3 comprises a body I containing an inertia mass 2/4 of generally cylindrical form, guided in the body I and in a cover 3. The lower part i of the inertia mass 2/4 is formed with two diametral slots 5 and 6 (Figure 2), serving to accommodate four movable setting elements I, consisting of cylindrical discs rolling upon their edges or lateral surfaces. The inertia mass 2/4 is maintained in a position of rest by a ring or segment 8 similarmining the path of the movable setting elements l, which move upon the said ramps.

The inertia mass 2 is urged downwards by a force l5, for instance by a spring, not shown.

The mechanism described is assumed to be mounted in the axis of a gyration fuze, the nose of the fuze being directed upwards.

When at rest, the parts of the mechanism occupy the positions illustrated in Figures 1, 2 and 3. The movable setting elements I rest upon the base of the body I. By centrifugal force the split ring 8 can be opened out so as to liberate the inertia mass 2/4, while bearing against the body 5.

The mechanism described operates in the following manner: When the shell is fired, the movable setting elements are subjected to the following accelerations:

(1) At the moment of discharge, to an axial acceleration I I directed downwards, which urges all the movable setting elements 1 downwards and presses them upon the base of the body I, and to a centrifugal acceleration I2 directed radially, which urges all the movable setting elements I outwards and presses them against the first ramp 9, as indicated in Figure 3.

(2) On leaving the muzzle, to the centrifugal acceleration I2 and to an acceleration of retardation i3, that is to say, to a relative acceleration, directed upwards, occasioned by the resistance of the air to the flight of the projectile.

From the time of leaving the muzzle, and under the action of the two accelerations I2 and I3, the movable setting elements I, which have been resting upon the base of the body I, roll upon the first ramp 9, and then quit this first ramp 9 and engage upon the second ramp l0, finally coming to bear against the upper portion 2 of the inertia mass 2/4 (Figure 1). The movable settin elements I now occupy positions similar to that represented at M, hatched horizontally.

While then ascending the second ramp I0, the movable setting elements raise the inertia mass 2/4 against the action of the force I 5. The movable setting elements I then occupy positions such as that of the element It represented in dotted lines in Figure l, and the inertia mass has risen to the extent represented by the distance ll.

The raising of the inertia mass may effect the setting of the fuze either directly or indirectly, or may effect any desired operation.

The ascent of the movable setting elements '0 along the ramp 9 is a function of the following magnitudes:

The centrifugal acceleration l2;

The retardation acceleration It;

The coefficient of rolling friction fr;

The diameter d of the elements; and

The slope of the angle of inclination of the first ramp, that is to say, the n le that th first ramp makes with the axi of the fuze.

The angle 18 that the first ramp 9 makes with the axis E9 of the fuze is illustrated in Figure 3. As the movable setting elements '1? roll up the first and second ramps, the centre of the element traverses the path represented by the dot-anddash line 25.

The coefiicient of rolling friction is very small, and may be about 0.0005 to 0.001. The retardation acceleration is in general small in comparison with the centrifugal acceleration, but owing to the coemcient of rolling friction being small, the rolling movement of the elements is possible when the angle it, that is, the inclination of the first ramp to the axis of the fuze, is only a few degrees.

The calculation of the movement of the movable setting elements I rolling upon the first ramp 9 shows that it is possible to obtain, for the displacement of the elements from the starting position 2! (Figure 3) to the position 22 at which the element leaves the first ramp, times of the order of a thousandth of a second, these times being a function of the length of the first ramp. It follows that it is possible, by means of the mechanism described, to obtain securitie of trajectory of a few metres, for instance five to ten metres according to the initial velocity of the projectile.

The mechanism will be so dimensioned that the axial acceleration i I will always be greater than the centrifugal acceleration l2, so that even in the case of firing below the horizon the movable setting elements will be urged, upon discharge of the shell, towards their initial position 2 l, on the base of the body I.

It has been stated that the angle of inclination it of the first ramp may have a value of only a few degrees. In practice this angle will be less than 5 degrees, and may even be less than 3 degrees. eration i3 is great enough in comparison with the centrifugal acceleration l2.

The angle of inclination l8 will be chosen at the minimum value that. will furnish maximum security of trajectory, but will at the same time be sufficient for the operation of the mechanism to be certain,

The mechanism described comprises setting elements which are displaced over the first ramp by a rolling motion.

A similar mechanism utilising elements that are displaced over the first ramp by a sliding movement would furnish practically no security of trajectory. In this case the tangent of the angle of inclination on the first ramp would have to be greater than the coefficient of sliding friction. For a coefficient of friction of 0.17 the angle would have to be greater than 10 degrees. In order to be sure of the mechanism functioning it would be necessary to make it slightly greater It might be zero if the retardation accelthan this, and tests have shown that in this case the elements are displaced practically instantaneously, and do not furnish any security of trajectory. Moreover the coefficient of sliding friction depends upon the condition of the sliding surfaces, which is practically not the case for the coeiflcient of rolling friction.

The mechanism according to the invention will therefore furnish securities of trajectory having very little dispersion, or in other words very great regularity of operation, whether the surfaces upon which the movable setting elements 1 roll, or the surfaces of the first ramp 9, are dry or lubricated.

In the mechanism described as movable setting elements use has been made of cylindrical discs lodged in radial slots in the part d of the inertia mass 2/ l. It is likewise possible, without going outside the scope of the invention, to provide an inertia mass 2/4 in two parta'the part #3- of the inertia mass, provided with the slots 5 and 6 then admitting of being stationary and serving only to guide the movable setting elements l, which may diminish the mass of the inertia mass 2.

When balls are utilised as movable setting elements it is possible to eliminate the guidance, to omit the part a of the inertia mass 2/15, and to retain only the upper part 2, which is shown hatched in Figure 1.

In order to ensure the operation of the mechanism described, it is necessary that the angle of inclinationof the beginning of the ramp should be greater than a predetermined minimum, so that the movable setting elements 1 may be able to start their journey.

In order to increase the accuracy of the trajectory a ramp such as that shown in Figure 4 may be utilised. The initial angle 23 has a predetermined value at the maximum slope, and the slope or angle of inclination of the ramp diminishes along the ramp, finally attaining a value 24 which is less than the angle 23 and which may be zero, or even negative.

The transition from the first ramp to the second may either be effected by an angle 25, or may comprise a rounding.

The slope of the second ramp is greater than 12 degrees.

Figure 5 is a diametral sectional view of a selfdestroying percussion fuze of a rotating projectile with predetermined delay action. A substantially cylindrical setting mass 3%i3l is adapted to slide by its upper part in the axially bored fuze body 3i. This mass 3fi-3l' carries on its rear part 3'! four longitudinal resting legs 66 separated from one another by parallel sided, radial slots 3339 (Fig. 6), symmetrically disposed around the axis of the fuze body 3 I. The bottom of each slot 38--3 9 serves as an axial abutment on the setting mass. an axial hole 45 for the passage of a stem is of a plunger or push-piece l6l'i the head t! of which is guided in the fuze body 3!. The inertia mass 36/3! is urged downwards by a helical spring 48. It is held in its idle position by a spring ring 49 split like a piston ring. The fuze body 3| is closed at the top by a sealing disc 50 and at its bottom or rear end by a plug 32 axially perforated for the passage of, the firing pin 35 of a striker ti/SE. This plug, provided with the usual recess for a primer, is formed on its upper face, around its axial perforation, with a cup 33 in which are lodged, at rest, locking balls 34. The striker 35/6! is provided with a bearing The inertia mass 36/3? has collar 6| engaged, at rest, between the rear end of the resting legs 60 and the locking balls 34.

A ring 4| is coaxially fastened to the fuze body 3| around the said resting legs 60. The inner cross section of this ring increases from its rear end, near the collar 6| of the striker, to its fore end so as to form by its rear part a substantially conically shaped rolling race 42, the average slope of which with respect to the axis of the fuze being very small, such that the said race is almost cylindrical. On account of its increasing inner cross section, the ring 4| comprises at its fore end a conically shaped working surface 43 the slope of which is much greater than that of the rolling race 42 with respect to the axis of the fuze.

Four movable setting elements 43, consisting of circular fiat discs are laterally guided by their fiat opposite faces in the radial slots 33-33 and are supported, at rest, by the bearing collar 6| of the striker. The discs 40 are adapted to roll by their edges on the conical race 42, owing to the combined action of the centrifugal force and a force due to axial retardation of the fuze after leaving the muzzle at firing. The whole axial length of the resting legs 63 and of the rolling race 42 on the one hand, the arrangement of the working conical surface 43 with respect to the bottom 93 of each radial slot 38/39 and the diameter of said discs 40 on the other hand, are determined in view of getting the desired delay period as will be hereinafter explained.

The fuze described operates in the following manner: when at rest, the parts take the positions represented in Figure 5. The striker 35/6l is locked by the balls 34 and cannot effect the percussion. Upon discharge of the shell the movable parts are urged rearwards on account of the acceleration of the projectile, particularly the discs 40 which are strongly applied against the collar 6| of the striker 35. By centrifugal force the spring ring 49 opens out and releases the inertia mass 36/31.

On leaving the muzzle after firing, under the combined action of the centrifugal force and a force due to the axial retardation of the fuze body, namely through the resistance of the air, the setting discs 40 roll upwards along the conical rolling race 42 and reach the working surface #13, where the centrifugal force impelled to said discs abruptly increases on account of the greater slope of this surface 43. A very short time afterwards, the setting elements 43 strike the bottom 90 of the radial slots 38/39 and begin to raise the setting mass 33/3! against the resistance of the spring 48. The time required for the discs 40 freely rolling on the race 42 until reaching the bottom of the radial slots 38/39 corresponds to the major portion of the desired delay period.

It should be noted that the centrifugal acceleration is impelled to the discs 40 through the resting legs 69 during the time spent from the instant of firing to the instant at which the fuze leaves the muzzle. At this latter instant, the speeds of rotation of the ring 5| and of the discs 46 about the axis of the fuze body 3| are practically equal and the rubbing of the faces of the discs 40 on the radial slots 38/39 is therefor very small.

The balls 34 that were locking the striker, being now urged radially under the action of the centrifugal force, raise the striker and move into the entries 44 in the rear end of the ring 4 I. The striker 35/61 is thus released and the fuze is set.

Preferably the setting is achieved only by the 6 movable setting elements 40. However, it may be assisted for a reduced proportion, as soon as the inertia mas 36/31 begins to move, by the locking balls 34 acting upon the rear end of the resting legs 60, but the balls 34 alone cannot effect the setting of the fuze.

The fuze being set, it functions as a percussion fuze, any encounter with an obstacle causing the destruction of the disc 53, the displacement of the push-piece 41 downwards, and the forcing of the striker 35 against the primer, not shown.

The movable setting elements 40 are maintained in a position of equilibrium upon the second ramp 43 by centrifugal force, against the thrust of the spring 48. By the retardation of the projectile upon its trajectory its speed of revolution is diminished, the centrifugal acceleration likewise diminishes, and the centrifugal force acting upon the movable setting elements 42 decreases. When its axial component reaches a value less than the force of the spring 48, the spring 48 impels the inertia mass 33/37 which effects the percussion and occasions the autodestruction of the projectile upon its trajectory.

The movable setting elements 40 of the fuze' described likewise serve as movable elements for auto-destruction.

It will be preferable to utilise, as movable setting elements, cylindrical discs 5|, of axis 32, as illustrated in Figure 8, but it is likewise possible, without going outside the ambit of the invention, to use balls for this purpose, or, more generally, solids of revolution.

Cylindrical discs rolling upon their edges or lateral surfaces have an important advantage over balls for example.

The first ramp consists of a frusto-conical surface, the generatrix of which forms an angle of a few degrees with the axis of the cone. The radius of curvature of the cone increases in the direction of rolling of the movable setting elements. In order to obtain a maximum area of contact surfaces between the movable setting elements and the ramp, cylindrical discs will be utilised in which the profile of the convex lateral surface has a radius of curvature equal to the minimum radius of curvature of the cone forming the first ramp. Such a disc is illustrated at 40 in Figure 6. The profile of its convex lateral surface 53 has a radius of curvature equal to the minimum radius of curvature of the cone forming the first ramp.

It is in fact impossible to give balls the minimum radius of curvature of the cone.

The increase in the area of contact surface increases the security of operation, enables the slope of the first ramp to be diminished, and thus procures a greater security of trajectory.

It will be advantageous to make the setting discs of non-ferrous metal, such as brass for example.

What I claim is:

A mechanism for delayed setting of a fuze in rotating projectiles, comprising: a fuze body; a setting mass axially slidable in said body and having an axial bore; said setting mass comprising a slotted rear portion having a plurality of radial slots, the bottom of each slot forming an abutment on said setting mass; spring means in said body for urging said mass backwards; a plug in the rear of said body and having an axial hole and a recess; a primer in said recess; a striker guided in said axial bore and in said axial hole; a transverse collar on said striker, said collar supporting said setting mass at rest;

a ring coaxial with said striker inside said body around said slotted rear portion and forward of said collar; the inner diameter of said ring increasing from its rear end to its fore end, the inner surface of said ring forming a rear conical rolling race of small angular slope with respect to the axis of the fuze and a fore conical surface of relatively greater angular slope; movable fuze setting elements having surfaces of revolution disposed and guided in said radial slots forward of said collar; said inner surface of said ring forming a rolling track for said setting elements, said setting elements abutting the fore surface of said collar during the initial rotation of said fuze; said rear conical race of the ring and said slotted rear portion having axial lengths greater than the diameter of said setting elements; said setting elements being freely movable on said rear conical rolling race, forward of said collar, for a predetermined time under the combined action of the centrifugal force upon accelerated gyration of the fuze and of their own inertia; said setting elements being thereafter adapted to roll on said fore conical surface. whereby to contact the bottom of said slots and to act on said setting mass against said spring means for setting the fuze; locking means rearward of said collar for holding said striker away from said primer before the setting of the fuze; said locking means and said setting elements being constructed and adapted to cooperate to release said collar, said striker and said setting mass by escape from said collar and from said abutments respectively only upon the action of said setting elements on said setting mass.

JEAN ROSSELET.

References Cited in the file of this patent FOREIGN PATENTS Number Country Date 43,453 France Mar. 19, 1934 859,089 France May 27, 1940 108,622 Sweden July 29, 1943 

